1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
An image forming apparatus using the electronic photography is generally constituted to include a photoreceptor which is a rotating image bearing member, and a charging section, an exposure section, a developing section, a transfer section, a fixing section, a cleaning section and a deelectrification section, which are arranged around the photoreceptor. The charging section charges the surface of the photoreceptor uniformly. The exposure section exposes the photoreceptor surface charged, to light according to image information thereby to form an electrostatic latent image. The developing section agitates and charges the toner so that a toner image is formed by adhering the frictionally charged toner to the electrostatic latent image formed on the photoreceptor surface. The transfer section transfers the toner image to a recording medium by charging the recording medium into the polarity reversed from that of the toner. The fixing section fixes the transferred toner image on the recording medium by, for example, heating and pressurizing. The cleaning section recovers the toner which is not transferred to the recording medium but left on the photoreceptor surface. The deelectrification section carries out deelectrification of the photoreceptor in a state where the toner image has been transferred therefrom. By the image forming apparatus using the electrostatic photography thus constituted, a desired image is formed on the recording medium.
This image forming apparatus is equipped with a toner supply section for supplying the toner to a developer container which is a container belonging to the developing section for containing the toner, because the toner used for the development in the developing section is consumed. The toner supply section supplies the developer container with the toner in the toner cartridge which is usually constituted so as to be attachable to and removable from the image forming apparatus. When the toner in the toner cartridge is exhausted as a result of the supply to the developer container, the image forming apparatus interrupts its actions. By replacing the toner cartridge having its toner exhausted by a new toner cartridge, however, the image forming apparatus is supplied with the toner so that it can perform again the image forming actions.
In recent years, there has been developed an image forming apparatus such as a copier or printer of electronic photography, which is intended for heavy users to consume much toner. In this apparatus, as much as toner is contained in one toner cartridge thereby to reduce the number of exchanges of the toner cartridge. When this large-sized toner cartridge containing much toner is used, the number of exchanges can be reduced to interrupt the image forming actions less frequently. It is, therefore, desired to lighten the burden on the user unfamiliar to the handling of the apparatus.
When much toner is contained in one toner cartridge, the number of interruptions of the image forming actions can be reduced by reducing the number of replacements of the toner cartridge. At the time of replacing the toner cartridges, however, it is impossible to avoid the interruption of the image forming actions. As a technique for solving this problem, there has been proposed an image forming apparatus (in Japanese Unexamined Patent Publications JP-A 8-137227 (1996) and JP-A 2003-208007, for example), which is equipped with a plurality of toner cartridges for containing toner of an identical color and which uses the (continuous run) system for automatically replacing the toner cartridge to be supplied with the toner.
The image forming apparatus, as disclosed in JP-A 8-137227, is equipped with a plurality of toner cartridges for storing the toner of an identical color, and toner transfer conduits connected to the plural toner cartridges and merging midway to transfer the toner discharged from the toner cartridge to the inside of the developer container. In the image forming apparatus disclosed in JP-A 8-137227, the toner is supplied from one of the plural toner cartridges. The toner can be supplied, when exhausted in one toner cartridge, from another toner cartridge so that its supply does not interrupt the image forming actions.
In the image forming apparatus disclosed in JP-A 2003-208007, on the other hand, the color image forming apparatus is equipped with a plurality of toner cartridges for a black color to be more consumed than the color toners of yellow, magenta and cyan, and the black toner cartridges are arranged in one row adjacent to each other. According to this image forming apparatus disclosed in JP-A2003-208007, the plural black toner cartridges can prevent the interruptions of the image forming actions from being frequently caused by the exhaustion of the black toner. Since the plural black toner cartridges are arranged in one row adjacent to each other, it is possible to spare the space for the toner containing portion and not to mistake the positions for mounting the toner cartridges.
Here in this image forming apparatus, after the toner cartridge mounted on one toner cartridge mounting portion was used to the last, this mounting portion may be loaded with the toner cartridge before the end of use, which has been employed in another image forming apparatus, or the toner cartridge which has been stored in the unconsumed state. The toner cartridge before the end of use is desirably employed as early as possible, because the toner contained therein is degraded in the charging characteristics and fluidity by the environmental influences such as humidity after left unused for a long time.
In the image forming apparatus disclosed in JP-A8-137227 and in JP-A 2003-208007, the toner cartridges mounted on the two toner cartridge mounting portions are constituted such that they are alternately employed for their individual mounting portions. In case the two mounting portions are provided, which are individually equipped with the toner cartridges, when the toner cartridge of one mounting portion is used up, the toner cartridge of the other mounting portion is employed. While the toner cartridge of the other mounting portion is being employed, the toner cartridge of one mounting portion is replaced by new one. In case this replaced toner cartridge is before the end, this toner cartridge before the end is not employed till the toner of the toner cartridge mounted on the other mounting portion is exhausted.
In the image forming apparatus disclosed in JP-A 8-137227 and JP-A 2003-208007 thus constituted, the toner cartridges mounted in the individual mounting portions are alternately employed for the individual mounting portions, but no consideration is taken into the used situations of the toner. In order to employ the toner cartridge before the end to be earlier employed, therefore, the complicated procedure is required for exchanging the unused toner cartridge to be mounted on the other mounting portion and the toner cartridge before the end of use. During this replacing procedure, moreover, there occurs a time period, for which none of the toner cartridges is mounted, to raise a problem that the image forming actions are interrupted.